The present invention relates to an improvement to measuring systems for measuring the relative position of two objects, of the type comprising a transducer for converting a mechanical input into an analog electrical signal.
In such measuring systems, which include a mechanical-electric transducer, the mechanical input can represent a path, an angle, a force, a pressure, a tension, and the like. Such transducers are operated for example on a photoelectric, inductive, capacitive, or piezoelectric basis. Certain transducers require an auxiliary energy source, such as the light source required by photoelectric transducers for example.
German Pat. No. 27 51 757 discloses a known photoelectric transducer which utilizes a light source to emit optical radiation and includes an element movable perpendicularly with respect to the direction of the optical radiation. A differential photosensor is positioned to sense the intensity of light modulated by the movable element. A zero position is established, from which light intensity directed upon the differential photosensor can be changed. An evaluating circuit which can be used to recognize the zero position of the movable element in such a photoelectric system is disclosed in German DE-AS No. 12 73 210. In this evaluating circuit two photosensors in combination with two similar resistors form a bridge circuit which is acted upon with a direct voltage. The bridge circuit includes a diagonal branch in which is placed a zero point detector.
The accuracy and precision of such transducers is in general limited by drift effects such as electrical parameters of component elements which change as a function of variations in temperature and aging.